1. Field of the Invention
The invention relates to an image processing apparatus and method of the same, for increasing the contrast of an input image in a display system.
2. Description of the Prior Art
Contrast stretching typically means to extend the range of gray scale level to the maximum gray scale level 0˜255 of a monitor, so as to increase the dynamic range of the distribution of the gray scale level of image and to further enhance the contrast of the image.
Please refer to FIG. 1, which illustrates a histogram of image characters. Conventional image contrast stretching technology first analyzes the distribution of the gray scale level of an inputted image, and then it generates a histogram of image characters of the inputted image as shown in FIG. 1. Then, the maximum gray scale level (Max) and the minimum gray scale level (Min) of the histogram is defined respectively. Take Photoshop as an example; the maximum gray scale level is defined to be the gray scale level corresponding to the 0.5% of the area from the right of the histogram, and the minimum gray scale level is defined to be the gray scale level corresponding to the 0.5% of area from the left of the histogram. For a color image, the maximum gray scale level means the maximum gray level among the red, green, and blue color (RGB), whereas the minimum gray scale level means the minimum gray level among the red, green, and blue color (RGB). Furthermore, the image contrast stretching is calculated via the following equation:Gray′=k*(Gray−Min)  Equ. 1
Wherein k=255/(Max−Min), Gray represents the gray scale level of the inputted image, and Gray′ represents the gray scale level after image contrast stretching.
According to the diagram of image characters, when the maximum and the minimum gray scale level are applied in the image contrast stretching, part of the larger and smaller gray scale levels (as shown by arrow a and b in FIG. 1) will be ignored, and details of dark and light zones will disappear. In the prior art, dynamic Gamma contrast enhancement technology is applied to enhance the details of dark and light zones. However, because the method hereinbefore is a dynamic process, it needs many Gamma look-up tables and further exhausts a large amount of hardware resources.
Accordingly, the major aspect of the present invention is to provide an image processing apparatus and method of the same to overcome the problems as described above.